Brightness discrimination in reflected laser light

Brightness discrimination judgments for gray chips were made by 12 male human Ss using the psychophysical method of limits. White, noncoherent red, and He-Ne laser light sources of equal power were used. The data showed poorer discrimination from white to red to laser light and better discrimination when trials started from the darker end of the stimulus range. Results are discussed in terms of human spectral sensitivity, masking effect of the standing diffraction pattern in laser light, and brightness contrast between the stimulus and surround.